Pictures: Spanish Solar Energy

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Pictures: Spanish Solar Energy

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An Early Focus on Solar

The sun-drenched swaths of land in southwestern Spain seem custom-made for large solar projects. Add generous government subsidies to this hospitable climate, and the solar opportunity in regions like Andalusia and Extremadura would seem almost too good to be true.

In fact, it was too good to last.

In the wake of an overheated solar market and the global financial crisis, Spain has slashed its renewable energy subsidies. And the solar boom under the Mediterranean sun has gone bust—a stunning reversal of fortune: In 2008, 40 percent of the world's solar installations were in Spain.

But it's hardly the end of the road for the technologies nurtured on the Iberian peninsula. Spanish companies are working to export their know-how to the United States, Latin America and even to other European Union nations.

Although the United States developed experimental solar power towers in the Mojave Desert in the wake of the 1970s energy crisis, it was nearly three decades later that Spain put the world's first commercial solar tower online in March 2007, 15 miles west of Seville in southern Spain's Sanlúcar la Mayor. The Planta Solar 10 solar tower plant, seen above with sunlight glinting at the top of its 377-foot (115-meter) tower, can provide electricity for as many as 5,500 homes and store energy for up to 30 minutes.

Like all concentrating solar plants, power towers use steam turbines to drive a generator to produce electricity. But developers long believed using circular rows of mirrors to focus the sun's rays on a central "power tower" would be more efficient than other types of reflector arrays, and would make it easier to integrate technology to store energy.

From a distance, the result is an otherworldly scene akin to a high-tech crop circle or an alien amphitheater. Up close, the projects resemble fields of giant mechanical sunflowers craning their shiny faces toward a glowing tower.

The plant uses 1,255 mirrors positioned across 210 acres to concentrate sunlight on a receiver mounted on the central tower. Water pumped up the 160-meter (541-foot) structure and through the receiver boils into steam. This steam is used to turn a turbine to produce electricity.

The two Planta Solar plants are part of the Solúcar Solar Complex, a 1.2-billion euro ($1.6 billion) project that supplies electricity for 94,000 households and sprawls over 1,000 hectares. The complex is also home to Abengoa research facilities and a trio of solar plants using parabolic trough technology.

And Abengoa is exporting its technology. Late last year, the Spanish company secured a $1.2 billion loan guarantee from the U.S. Department of Energy for a solar plant in southern California using its parabolic trough technology. The Mojave Solar Project is aimed at increasing solar thermal power capacity in the United States by 50 percent. Abengoa has pledged to get 80 percent of the parts for the project from U.S. suppliers.

The PS10 solar power tower near Seville produces electricity using 624 dual-axis mirrors, known as heliostats, which track the sun and reflect sunlight onto receivers at the top of the tower. Each heliostat measures 120 square meters (1,291 square feet), and the whole solar field occupies 140 acres.

Abengoa Solar developed its tower technology in collaboration with the Spanish government's Ciemat (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas) and Germany's DLR aerospace research center (Deutsches Zentrum für Luft- und Raumfahrt), as well as universities.

The world's first round-the-clock solar power plant, Gemasolar Thermosolar Plant in Fuentes de Andalucía, Spain, opened last year. It can generate electricity day and night, and no matter what the weather, by using molten salt to transfer and store heat captured from the sun. The liquid salt, which can reach temperatures hotter than 500°C (932°F), allows electricity generation for as long as 15 hours without sunshine. The design uses heat to generate steam, which is directed to a turbine to produce electricity.

In the Mojave Desert, near the California-Nevada border in the U.S., a BrightSource Energy solar tower complex currently under construction also will use molten salt to store heat energy. The project is slated for completion in 2013. Meanwhile, a 540-foot solar power tower went up in early February in the desert near Tonopah, Nevada, for SolarReserve's project, Crescent Dunes, which aims to be the world's largest molten salt solar power plant, also slated for operation in 2013.

Torresol Energy owns the plant; it is a joint venture between Spanish construction and engineering firm Sener and the Abu Dhabi government's renewable energy company, Masdar.

Photograph by Markel Redondo for Greenpeace

Banking on Renewable Energy

Abengoa was able to secure financing for the sprawling PS10 project from Sabadell bank in 2004, after the Spanish government increased the tariff for solar thermal and allowed natural gas to fuel up to 15 percent of annual electricity generation.

Completed in May 2011, the Gemasolar thermasolar plant delivers electricity to the power grid in just a handful of steps. First, cold salts are pumped from a ground-level tank to the top of the tower, where they heat up in the sunlight receiver. Then the salts drop back down into another tank where hot salts are stored at 500°C (932°F) or more.

From there, the salts can be piped to heat exchangers. As the salts cool, released steam turns a turbine, and a generator produces electricity. That electricity goes to a transformer, and then to the electrical network.

Photograph by Markel Redondo for Greenpeace

Producing Gigawatts in Granada

Andasol 1 and Andasol 2 in Granada, Spain, feature parabolic trough technology. Connected to the grid since 2008 and 2009, respectively, the plants use long rows of parabolic mirrors, curved and tilted upward so that they look like troughs. This captures and concentrate solar irradiation, generating intense heat to produce steam. Steam turns a turbine, which is connected to a generator to produce electricity. Andasol 1 generates 175 gigawatt-hours per year.

Photograph by Markel Redondo for Greenpeace

The Shape of Solar Power

La Dehesa, a parabolic trough solar thermal power plant in Spain's Badajoz region, also uses molten salts for storage. Twenty-nine thousand tons of sodium nitrate and potassium nitrate store enough heat for the plant to generate electricity for up to 7.5 hours without sunshine. Developed, owned, and operated by Renovables SAMCA, the plant occupies 494 acres (200 hectares) of land and generates an estimated 170 gigawatt-hours per year.

Photograph by Markel Redondo for Greenpeace

Expanding a Long Stretch of Solar

Andasol 1 and 2 were joined by a third plant, Andasol 3, in summer 2011, after three years of construction. With an installed output of 50 megawatts, the new plant collects sunlight using some 205,000 parabolic reflectors. Molten salt storage tanks allows the plants to generate electricity for up to 7.5 hours without sunshine.